Alloy steel and method of producing the same



Patented Nov. 16, 1926.

UNITED STATES PATENT OFFICE.

' HARRY B. KIl INNEAR, OF MARION, OHIO, ASSIGNOR TO THE MARION STEAM SHOVE L COMPANY, OF MARION, OHIO.

ALLOY STEEL AND METHOD OF PRODUCING THE No Drawing.

This invention relates to an alloy steel and theimethod of producing the same and itis designed moregparticularly for use in the production of steel castings.

One object of the invention is to provide a high tensile steel having an unusually high elastic ratio with suitable ductility.

A further object of the invention is to pro vide a steel forcastings which will be of a hard "tough character but will be easily machined; and which will have a relatively low shrinkage.

A further object of the invention is to provide such a steel which can be easily produced at a relatively low cost.

In carrying out the invention I first modify the, constituent elements of'the usual steel by adding thereto a quantity of copper. The steel which forms the basis of the alloy may be of any suitable character and may be produced by any suitable process. The other constituents of the steel are those usually present and while the percentage of the various constituents may vary the followingrange of percentages is a desirable one: carbon 20% to .60%; manganese .60% 'to .90%; sulphur and phosphorus under .05% and silicon 20% to .60%. The copper may be added to the steel either before or after melting and the percentage of copper -which is contained in the alloy may vary greatly. Ordinarily" the percentage of copper ranges from .50% to 5% and highly satisfactory results are obtained by the use of approximately .90% of copper. 'It will be understood, however, that the quantity of copper is not limited to the range of percentages here mentioned as the amount of copper may be very greatly in excess of 5% and may be less than .50%, this being determined, in part atleast, by the character of the steel to which the copper is added and by the physical properties of the alloy which it is desired to obtain.

The molten metal is poured and the ingot or casting formed in the usual or any suitable manner. state, that is as it comes from the mold, is not ductile to any large extent and while its ultimate strength is comparatively high its elongation will in many instances low, depending .upon the carbon content. I have ,found, however, that proper heat treatment greatly "changes the physical The alloy metal in the raw Application filed December 30, 1925. Serial No. 78,386.

properties of the steel and increases the yield point, ultimate strength, elongation, reduction of area and the Brinell hardness to a marked degree, thereby producing a hard steel having great strength and high elastic ratio and which can be easily machined. The manner of heat treating the castings may vary but I prefer to first normalize the casting by heating the casting to a relatively high temperature and then cooling the same slowly, preferably in air, and to then draw the normalized casting, that is, to re-heat it and again cool it slowly, as in air. In normalizing the casting the most satisfactory results have been obtained by heating the casting -to approximately 1550 degrees F.- for a time suflicient to insure the entire mass reaching this temperature, holding the same, at this temperature for a relatively short period and then coolingiin air. This treatment transforms the alloy into a ductile, easily machinable material having high ultimate strength and high elastic ratio. It will be noted that the temperature to which the casting is heated in the normalizing operation is low, as the ordinary carbon steels and many of the alloy steels require a temperature of from 1700 degrees F. to 1750 degrees F. to break up the original dendritic structure and produce a fine grained product. This low temperature has obvious advantages. It not only results in a material saving in time and fuel.

in the normalizing operation but it greatly reduces the scaling action which is encouncooled. .The drawing of the casting as described after normalizing increases the yield point, ultimate strength, elongation, reduc tion of area and Brinell hardness, all to a marked degree. It is -a well known fact that after air quenching or normalizing the usual carbon or alloy steel is let down by re-heating, that is, the yield .point, ultimate strength and Brinell hardness decrease on re-heating. lVith the present alloy steel these physical properties are increased on re heating. To illustrate the effectof the heat treatment on the steel the following example may be electric furnace given. Test bars from an heat of this alloy steel analyzing carbon .40; manganese .74; silicon .41; copper .88; phosphorus .039; and sulphur .014, were heat treated, machined and pulled with the following results. When normalized at 1550 degrees F. the yield point was 67 500; ultimate strength 102750; elongation 13.5; reduction or area 1 9.3; Brinell hardness 207. \Vhen normalized at 1550 degiees F. and then drawn at 1000 degrees F. the yield point was 812 50; ultimate strength 114700; elongation 18.0; reduction of. area 21.3; and Brinell hardness .228.

This increase in the yield point, ultimate strength, elongation, reduction of area and hardness, which results from the heat treatment, is important not only because of the highly desirable physical properties of the finished casting but also because of the fact that it makes posslble the production of castings, meeting different specifications, from a single grade "of metal. The normalized casting will in many instances have the physical properties necessary to meet one set of specifications without drawing the same, and, when drawn, castings from the same metal will have difl'erent physical properties which will meet the requirements .of a second specification. Further, if the material is off in analysis and cannot be made to meet the first specifications by ordigr nary normalizing it may be drawn and'in this way the yield and tensile raised to meet the specifications, and the castings thereby salvaged.

' A further advantage which results from this alloy steelis found in the fact that the copper contained in the scrap is not lost but remains in the melted down, so that it is not' necessary to add copper to the full percentage required to add that amount of copper steel, will aggregate the desired percentage. Further, this alloy when cast has a remarkably low shrinkage, thus enabling castings of difierent sections to be produced without excessive loss.

While a steel having the several physical properties above set forth is best produced,

the particular method described, it will be understood that this .method may be varied and castings produced at a low cost,

which have very valuable physical properties- For example, by first heating the casting and quenching the'same quickly, asin water, and then drawing the same a very bath of metal, when.

hard tough casting is roduced, which while not having all the p ysical properties of the castings produced by the first mentioned method, will nevertheless give just as sat,-

dsfactory results as the usual high priced steels. Again, by heating the raw casting and cooling in the furnace a verylarge degree of ductility may be had which will enable castings so treated to beused in places which now require a special low carbon steel.

Thus it will be understood that my invention, in its first or larger aspect, comprehends thesproducti'on of a steel alloy formed by combining, in a molten state, steel, in the bined with the steel when normalized at approximately 1550 F. I My invention, in its further or next aspect, combined 'wlth the above aspect, comprehends the step of re-heating the normalized.

product within the range of temperatures stated above as between approximately 950. F. and approximately 1025 F. followed by a cooling step; by which re-heating I obtain the further qualities in the product of a greater increase in the elastic limit, a greater increase in the tensile strength and also a eater degree of Brinell hardness as comthose obtained without the repared with while the latter I obtain heating step, also an increase in in the elongation. J 7

And finally, my invention, in its remaining aspect, comprehends the composition, which I subjected to these ste s of treat' ment, composed of steel, pre erably that which is known as carbon steel, combined with copper from approximately one-half of one per cent up to approximately five per cent.

I have referred more particularly, in the foregoing description, to castings, but it will be understood that the alloy steel may be poured in ingots and then worked into finished parts, by forging, rolling or the like, and the finished parts will respond to the described heat treatment in the same manner as the castings, and the term casting as "herein employed is intended toinclude parts so formed as well as those which are given their final. shape in a mold.

Further, I have found that the addition of copper to iron will produce an alloy having very valuable physical properties.

the reduction of area and Having now fully described my inven-' tion, what I claim as new and desire to secure b Letters Patent, is: I

. 1. T e method of treating an alloy. steel of" a particular composition, to-wit, steel combined with cop er, the latter in quantity from approximate y one-half of one per cent up to approximately five per cent, which method comprises these steps, namely, combining the steel and copper by a melting heat; curing an ingot or castin from such' mol ten mass; normalizing sai ingot or. casting by suflicient heat less than 1700 degrees F. continued until the entire massis reached and by cooling such ingot or casting.

2. The method of treating an alloy steel of a particular composition, to-wit, steel combined with copper, the latter in quantity from approximately one-half of one per cent up to approximatel five per cent, which method comprises t ese stepsfnamely, combining the steel and copper .by a .melting heat; pouring an ingot or casting from such molten mass; normalizing such ingot or casting by heating it to approximately 1550 F. for a sufiicient time to insure the entire mass being reached by the heat; air-cooling such ingot or casting; reheating such ingot or casting at a temperature between approximately 950 F. and. approximately 1025 F.; and again air-cooling such ingot or casting.

3. The method of treating an alloy steel of a particular composition, to-wit, steel combined with copper, the latter in quanwhich method comprises these steps, namely,

combining by a melting heat carbon steel containing substantially .20 per cent to .60 per cent of carbon, .60 er cent to .90 per cent of manganese, und e v sulphur and phosphorus, and .20 per cent to .60 per cent oflsilicon, with approximately one-half of one per cent up to approximately five per cent of copper; pouring an ingot or castin from such molten mass; normalizing suci ingot or casting by heating it to approximately 1550 F. for sufiicient time to insure the entire mass being reached by the heat; air cooling such ingot or casting; re-heating such' ingot or casting at a temperature between 950 F. to 1025 F.'; and in again air cooling such ingot or castinlg. 4. he method of treating an alloy steel of a particular composition, to-wit, steel combined with copper, the copper being in quantity from approximately one-half of one per cent'to approximately five per cent,

to increase the tensile strength, the elastic limit and the Brinell hardness, which method consistsiin normalizing such alloy by suflicient heat.- continued until the entire mass is reached; in re-heating it to approximately I000 F.; and in cooling it.

In testimony whereof, I aflix my signature hereto.

HARRY B. KINNEAR.

r .05 percent of' 

